1. Field of the Invention
The present invention relates to a method for controlling destructive pest infestations. More particularly, the invention relates to a new chemical formulation and a novel method of application to wood structures for combatting termites and other pests and for providing a continuing repellant effect against further infestations.
2. Description of the Prior Art
The conventional methods for combatting insect infestations are sub-slab and perimeter soil injection, subsoil bait stations, and fumigation. Sub-slab and perimeter treatments involve injection of an insecticidal composition into the soil below or around the foundation of structures. Though effective when strong insecticides are used, these methods pose environmental hazards because of the toxicity of the chemicals injected into the ground, especially when the ground below the structure is porous, and/or when an aquifer is relatively close to the surface. Therefore, laws and regulations have severely limited the ability to use the most effective pest-control agents, such as Chevron's Chloradane.RTM.. Moreover, dispersal of the insecticidal active ingredients in the environment through runoff and natural breakdown gradually reduces the effectiveness of the treatment in preventing further infestations.
Soil treatment methods involve the application of a chemical termiticide to the ground around the foundation of a structure. The goal of this application is to create a barrier that kills any termites coming into contact with it, thus preventing their entry into the structure. One major problem with using this method is the fact that the chemicals used tend to rapidly break down so that the barrier is ineffective within a relatively short period of time (2 years or less), prompting the need for expensive retreatment. Secondly, barrier treatments using soil termiticides generally do not affect populations of subterranean termite colonies (prevalent in hot, arid regions), which may be able to tunnel through or otherwise avoid the treated area.
The colony baiting methods of termite control typically involve adding a slow acting toxicant to a source of food with the idea of inhibiting the growth of or otherwise poisoning the entire colony. Limitations of the baiting methods revolve around the need for termites to first find, and then continue feeding on, the treated wood. If termites begin to avoid treated bait or if the entire colony is not eradicated, the termite population may in fact increase in or around the treatment area due to unchecked growth or to the foundation of supplemental colonies.
Fumigation involves the delivery of termiticides or other chemicals in aerosol form in an enclosure enveloping the building being treated. As such, it poses environmental problems resulting from chemical exposure to humans, animals and vegetation. Furthermore, fumigation leaves no residual and accordingly does not provide long-lasting protection.
Various pest-control and preservative compositions have been described in prior patents. For example, U.S. Pat. No. 5,196,407 to Goletz et al. (1993) discloses a composition comprising a fungicidal carbamate used for preserving wood and wood material. An insecticide may also be included in this composition. U.S. Pat. No. 5,207,823 to Shiozawa (1994) describes a wood preservative composition comprising copper borate and zinc borate as the active principles in a volatile basic carrier. In U.S. Pat. No. 5,089,483 (1992), Tsuda et al. disclose the use of alkyldimethylamine tetraborate as an effective antidecay and antitermite agent for timber.
A known class of useful pesticidal compounds consists of pyrethroids, synthetic substances related to pyrethrins. Characterized by a 2-phenyl-alk-1-enyl-cyclopropane-carboxylic acid ester core, pyrethroids include the effective insecticides bifenthrin and permethrin. U.S. Pat. No. 4,344,963, issued to Fuchs et al. (1982); European Patent Application No. 11,789, published Nov. 19, 1979; and UK Patent Application No. GB 2,038,636, published Jul. 30, 1980, all describe pyrethroids as useful insecticides and acaricides.
Building materials pretreated with borates are also known. U.S. Pat. No. 5,270,108, issued to Savoy (1993), discloses a building material with a foam core bonded to exterior skins of oriented strand board. The core is treated with a sodium borate compound to preserve the building material from insect, mold, and fungi attack. U.S. Pat. No. 5,373,674 to Winter (1994) describes another prefabricated building panel that includes an insulative core. Borate may be incorporated or encapsulated within the core.
In U.S. Pat. No. 3,858,346 (1975), Bailey teaches the combination of termite-attracting baits with the impregnation of exposed lower structure timbers with a liquid carrying a termiticide. Finally, in U.S. Pat. No. 5,346,699 (1994), Tiernan et al. disclose the concept of injecting a pesticide in foam form under the slab of a structure for the purpose of saturating the ground and all open passages to the structure from underneath the slab. The technique is directed to reaching and depositing active ingredients on the surface of all affected structural materials.
None of these inventions, taken alone or in combination, address the issues of treating the material in a building with the idea of not only exterminating the termites present at the sites but also repelling them from their food source to prevent future infestations. In addition, because of the necessity of contaminating the soil, no prior-art method is environmentally innocuous. Therefore, a need still exists for an environmentally sensitive, yet effective and long-lasting method for combating pest infestations in a manner that provides long-term protection against renewed attacks.